Present printing and continuous dyeing processes typically involve applying various dyes, treating with heat or steam to fix the dyes, washing to remove excess dye, and drying to remove the water introduced in the wash. In order to obtain high clarity and registration of the dyed pattern, it is necessary to set the dyes as quickly and completely as possible so that the various colors do not intermix. Examples of these processes are Kusters dyeing, silkscreen printing and the Millitron process. With the advent of computer-controlled printing processes, intricate multicolored designs, or "color graphics", for carpets, upholstery, pile fabrics, etc., are increasing in popularity. For these processes, it is especially important that the various dyes remain where they are deposited on the fabric and do not have a chance to migrate and mix. Thus, in order to achieve high pattern clarity and registration, it is necessary that the fabric have a high dye strike rate. It is also desirable to operate the dyeing process at room temperature to reduce energy costs by eliminating the expense of passing the fabric through a steamer to fix the dye.
Salt-blended copolymers of nylon 6 and nylon 6,6 are disclosed in U.S. Pat. Nos. 2,252,555 and 2,252,557, where they were reported to be useful in the preparation of clear films due to their low crystallinity and in making cold drawn fibers for use in the textile industry.
U.S. Pat. No. 4,729,923 discloses room temperature dyeable crimped polyamide fibers with small spherulites and a process of making such fibers from 1-6% nylon 6, 94-99% nylon 6,6 and 0.001-2% soluble inorganic metal salt, which preferably is calcium acetate.
U.S. Pat. No. 4,559,196 describes random copolymer yarns of nylon 6,6 and 6-12% nylon 6 wherein the dyeability of the yarns is enhanced by treatment with saturated steam at temperatures close to the melting point of the copolymer.